From IMPERIAL COLLEGE LONDON
The ozone layer – which protects us from harmful ultraviolet radiation – is recovering at the poles, but unexpected decreases in part of the atmosphere may be preventing recovery at lower latitudes.
Global ozone has been declining since the 1970s owing to certain man-made chemicals. Since these were banned, parts of the layer have been recovering, particularly at the poles.
However, the new result, published today in the European Geosciences Union journal Atmospheric Chemistry and Physics, finds that the bottom part of the ozone layer at more populated latitudes is not recovering. The cause is currently unknown.
Ozone is a substance that forms in the stratosphere – the region of the atmosphere between about 10 and 50 km altitude, above the troposphere that we live in. It is produced in tropical latitudes and distributed around the globe.
A large portion of the resulting ozone layer resides in the lower part of the stratosphere. The ozone layer absorbs much of the UV radiation from the Sun, which, if it reaches the Earth’s surface, can cause damage to DNA in plants, animals and humans.
In the 1970s, it was recognised that chemicals called CFCs, used for example in refrigeration and aerosols, were destroying ozone in the stratosphere. The effect was worst in the Antarctic, where an ozone ‘hole’ formed.
In 1987, the Montreal Protocol was agreed, which led to the phase-out of CFCs and, recently, the first signs of recovery of the Antarctic ozone layer. The upper stratosphere at lower latitudes is also showing clear signs of recovery, proving the Montreal Protocol is working well.
However, despite this success, scientists have today revealed that stratospheric ozone is likely not recovering at lower latitudes, between 60?N and 60?S (London is at 51?N), due to unexpected decreases in ozone in the lower part of the stratosphere.
Study co-author Professor Joanna Haigh, Co-Director of the Grantham Institute for Climate Change and the Environment at Imperial College London, said: “Ozone has been seriously declining globally since the 1980s, but while the banning of CFCs is leading to a recovery at the poles, the same does not appear to be true for the lower latitudes.
“The potential for harm in lower latitudes may actually be worse than at the poles. The decreases in ozone are less than we saw at the poles before the Montreal Protocol was enacted, but UV radiation is more intense in these regions and more people live there.”
The cause of this decline is not certain, although the authors suggest a couple of possibilities. One is that climate change is altering the pattern of atmospheric circulation, causing more ozone to be carried away from the tropics.
The other possibility is that very short-lived substances (VSLSs), which contain chlorine and bromine, could be destroying ozone in the lower stratosphere. VSLSs include chemicals used as solvents, paint strippers, and as degreasing agents. One is even used in the production of an ozone-friendly replacement for CFCs.
Dr William Ball from ETH Zurich and PMOD/WRC Davos, who led the analysis, said: “The finding of declining low-latitude ozone is surprising, since our current best atmospheric circulation models do not predict this effect. Very short-lived substances could be the missing factor in these models.”
It was thought that very short-lived substances would not persist long enough in the atmosphere to reach the height of the stratosphere and affect ozone, but more research may be needed.
To conduct the analysis, the team developed new algorithms to combine the efforts of multiple international teams that have worked to connect data from different satellite missions since 1985 and create a robust, long time series.
Dr Ball said: “The study is an example of the concerted international effort to monitor and understand what is happening with the ozone layer; many people and organisations prepared the underlying data, without which the analysis would not have been possible.”
Although individual datasets had previously hinted at a decline, the application of advanced merging techniques and time series analysis has revealed a longer term trend of ozone decrease in the stratosphere at lower altitudes and latitudes.
The researchers say the focus now should be on getting more precise data on the ozone decline, and determining what the cause most likely is, for example by looking for the presence of VSLSs in the stratosphere.
Dr Justin Alsing from the Flatiron Institute in New York, who took on a major role in developing and implementing the statistical technique used to combine the data, said: “This research was only possible because of a great deal of cross-disciplinary collaboration. My field is normally cosmology, but the technique we developed can be used in any science looking at complex datasets.”
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The paper: ‘Evidence for a continuous decline in lower stratospheric ozone offsetting ozone layer recovery’ by William T. Ball et al. is published in Atmospheric Chemistry and Physics.
How do they know that the ozone hole is healing? It was there the first time that they looked, and then they assumed that it had to be man made. Maybe the hole is supposed to be there, and if it closed it portends doom.
We live on a saltwater planet with chlorine, bromine, HCl in sea spray from waves pounding beaches and cliffs and wind blown from wave crests and hurricane conduits to the stratosphere. We have volcanoes and volatiles from plants, forests making chemical soup of the atmosphere, lightning strikes probably cleaving salt into sodium hydroxide/hydrogen and Cl gas.
Here is a Springer link article on analysis of volcanic gases
https://link.springer.com/article/10.1007/BF02596953
“The determination of H2O, CO2, SO2, SO2, S2, H2S, HCl, HF, H2, N2, O2, CH4, CO and NH2 is described.”
And: http://volcano.oregonstate.edu/book/export/html/393 .
“Once the tube is inserted into the fumarole or vent, the gases will bubble through the solution and gases like CO2, H2S, SO2, HCL and HF will dissolve into the liquid. Those gases that remain like N2, O2, H2, CO and He will rise further and collect in the headspace of the bottle.”
It seems to me that a hot mix of these gases, the very reactive HCL and HF (fluorine is the most electronegative element in the periodic table and therefore reacts with almost everything. It requires special plastic containers – it dissolves glass, rock, metals, etc. CO is similarly reactive – so you have all the ingredients in a very reactive hot gaseous state. I believe it would be a questionable presumption that no natural sources of CFCs exist as every article first in line on the internet tells us. And you know these “popular” articles are crazy-glued into place by nets of metadata. If you type whatsupwiththat in many search engines, the first place is Wikipedia – using the name and the header from WUWT and describing it as a site for science deniers! All the controversial stuff is voraciously guarded against employing sophisticated meta data algorithms to keep you away from what you are looking for.
the key words in the piece are “more research may be needed”. in other words funding may be running short and they want more of your money.
Watching the quietening of the sun esp UV-wise, we expect lower ozone production, but also lower destruction. The real story is likely to be quite different. The whole tale is a fable. Their mechanism lacks the right energetics for the proposed reactions. Here in the SH the claimed hole over NZ never happens, but they spin the scare story anyway.
Of course, the whole process is misdescribed, with shortages restricted to the winter polar darkness. Relax, the penguins and polar bears are safe from sunburn.
Remarks about some statements in the article.
“Ozone is the substance that forms in the stratosphere”. Incorrectly. Ozone forms also in the troposphere as a result of lightning discharges and (more important) of photochemical reactions: https://en.wikipedia.org/wiki/Tropospheric_ozone. Processes in the stratosphere can not be considered without taking into account the role of tropospheric ozone.
“It (ozone) is produced in tropical latitudes and distributes around the globe”. Wrong. Ozone can form in the stratosphere wherever there is available UV-radiation of sufficient energy. Formation of ozone stops only in polar regions during polar nights.
“In 1970s, it was recognized that chemicals called CFCs, were destroying ozone in the stratosphere”. The word “recognized” is irrelevant here, because M.Molina and F.Rowland (1974) did not prove experimentally chemical reaction between CFCs and O3 in the stratosphere, they “have attempted to calculate the probable sinks and lifetimes for these molecules” (CF2Cl2 and CFCl3). https://unep.ch/Ozone/pdf/stratopheric.pdf These authors considered raising CFCs to the stratosphere due to vertical diffusion, but did not take into account gravity (both substances are 4 – 4.5 times heavier than air) and the fact what CFCl3 to liquid state already at the temperature +23.6oC.
About the very short living substances. The most important are CHBr3 and CH2Br2 (boiling points are 149 and 97oC). Is it possible for them to reach the stratosphere?
Also, bond energy for C-Br is 276 kJ/mole, it corresponds to maximum wavelength for breaking bond of 434 nm. It means that VSLS can be destroyed in the lower troposphere, their effect on stratospheric ozone if doubtful.
Anybody notice that the time series of global atmospheric equivalent chlorine bears an uncanny resemblance to the time series of global temperature? Anybody stop and think that ionizing UV-B, which is well-known to produce severe sunburn and genetic alterations could also be a potent source of global warming? Anybody (besides me and Peter Ward) stop and think that the main forcing agent in global warming isn’t CO2 at all but chlorine from CFCs and non-explosive (non-erosol-producing) volcanoes?
It’s not CO2, stupid; it’s CHLORINE!
O’key, let’s think. UV-radiation Is a source of global warming. The ozone absorbs UV-radiation, so ozone depletion should lead to an increase in temperature. The largest ozone hole at the end of the last century was over Antarctica. However, in fact in Antarctica in these years there was cooling:
http://www.scienceagogo.com/news/20020015034521data_trunc_sys.shtml
The largest warming trend in the world between 1976 and 2000 was near ice-free portions of the Antarctic Peninsula. The high albedo of most of the continent beneath the ozone hole reflected away most of the incoming radiation.